Bolt or stud tightener



July 31, 1951 STONE 2,562,831

BOLT OR STUD TIGHTENER' Filed NOV. 12, 1946 IHIH llll 25 WWW INVENTOR ALBERT ymcyrom STONE g4 flq jr HIS A-NRNEY Patented July 31, 1951 UNITED smrrs BOLT OR STUD TIGHTENER Albert Rivington Stone, Baltimore, Md., assignor to Gerotor May Corporation, a corporation of Maryland Application November 12, 1946, Serial No. 709,201 Claims. (01. s1 52.4)'

My invention relates to bolt or stud tighteners, and more particularly concerns means for tightening bolts, studs, and the like to predetermined elongation and stress.

Among the objects of my invention is the pro- 5 vision of a bolt or stud tightener which while simple, sturdy, foolproof, compact and selfcontained, in itself admirably achieves the tightening of such bolts, studs or the like as heretofore described, and including self-contained gauge rods, through power-driven and automatically-controlled means, whereby the nut, stud or the like is quickly tightened down to the required extent as indicated by the gauge rod and this in rapid and absolutely accurate manner, all with the requirement of supervisory labor of but moderate skill,

Another object is to produce a tightener of the general type hereinbefore described which is comparatively inexpensive and displays long useful life.

Other objects will in part be obvious and in part more fully pointed out hereinafter in the course of the following description, taken in the light of the accompanying drawings.

My invention accordingly resides in the several parts, elements, mechanisms, features of construction'as well as in the combination of each of the same with one or more of the others, as described herein, the scope of the application of all of which is more fully set forth in the claims at the end of this specification.

In the drawings, wherein I have disclosed illustratively several embodiments of my invention which I prefer at present,

Figures 1 and 2 are companion sectional eleva--:. tions of a stud or bolt embodying a gauge rod measuring device, Figurel disclosing the unstressed bolt and Figure 2 showing it in stressed condition;

Figure 3v is a side elevation, partly in section, of my new power-driven tightener as applied to the bolt of Figures 1 and 2, certain parts conveniently being omitted;

Figure 4 is a top plan view taken from the right end of Figure 3; Figure 5 is a detail sectional viewon an enlarged scale, taken at the right end of Figure 3;

Figure 6 is a detailed fragmentary sectional viewsomewhat akin to Figure 3, disclosing the application of my invention to a hollow-headed screw, the measured elongation or stressing of which is desired; while,

Figure '7 is a view similar to Figure 6, but disclosing the application of my invention to the thereof.

2 running down and tightening of a nut on a stud or bolt.

Throughout the several views of the drawings, like reference characters denote like parts.

As conducive to a more thorough understandingof my invention, it may be noted at this point that considerable difficulty heretofore has been encountered. in the prior art in turning down and seating nuts, bolts, studs and the like to exactly predetermined torques. The field of application of this general manner of fastening is so diversified and generalized as to need no exemplification by way of illustration. Suffice it to say that efforts towards uniform tightening have been made by simply tightening an ordinary bolt or stud to a predetermined reading as evidenced by the indication on a torque wrench. As a refinement of this proposal a slip clutch has been .built into the torque wrench, which provides for slipping and constant non-functioning of the wrench when the predetermined torque value has been reached. Still another technique in common use has been to turn down the bolt,

through tests made by both automotive and aircraft technicians, that even in those instances where extreme care is employed in constructing the threads on the threaded members, and Where Q ample lubrication is employed during the tightening process, there may nevertheless occur a tension difference between two tightening elements of as much as Such error is obviously serious.

Precision work has necessitated the use, instead of blind end bolts or studs, the inner threaded end of which seats within the metal workpiece, of all-through studs which extend entirely through the workpiece on both sides Reasonably satisfactory results have been achieved and fairly uniform tensioning obtained when such all-through studs are employed in cooperation with a suitable snap-gauge.

obtaining comparable results in what may be termed blind-hole applications, wherein the threaded end of the bolt seats within the work piece, as a result whereof both ends cannot be reached by the snap gauge. My new power tightener is primarily intended for cooperation with my improved bolt or stud, described generally in this application and in greater detail in my copending companion application Serial No. 588,650, filed April 16, 1945, and entitled Fastening Device, now U, S. Patent 2,413,797 of January '7, 1947. My present invention combines all of the advantages of power tighteners with my improved bolt or stud.

Generally stated, my invention may be envisioned as comprising a tightener having a head portion which seats about or otherwise engages with the head of the bolt or stud, or grips the nut, as the case may be. Upon application of power thereto, this tightener turns down the bolt, stud or nut, thereby stressing it. A body portion serves to receive the energy from whatever source of power is employed, be the same fluid, mechanical or electrical in nature.

An adjustable micro-switch is employed, adjustableboth as to bolt elongation and bolt stressing. A follower extends through'the tightener and serves to cooperate with the pin in the bolt, stud or the like. ing the rod in the tightener to follow and maintain contact with the plum the bolt. Part of the micro-switch comprises a plunger which is in resilient and biased abutting relation to the end of the rod of 'the tightener and in the axial prolongation thereof. The function of the microswitch is to position the plunger thereof axially relative to the rod of the tightener and to bring it into stressed abutting relation thereagainst,

and as well, to tension to a predetermined extent a coiled or other suitable spring disposed between the micro-switch and the tightener proper. In this calibrated manner the spring causes the rod .of the tightener to follow the pin of the bolt down during the tightening process until finally sep aration occurs between the micro-switch plunger and the rod of the tightener. This automatically brings into. operation conventional control mechanism not shown which terminates the power impulse to the tightener. Tightening to an exactly predetermined extent is thus achieved.

And now, having reference more particularly to the construction shown in Figures 1 and 2, which in general is similar to that disclosed in my companion application, Serial. No. 588,650, hereinbefore referred to, now Patent 2,413,797 a bolt indicated generally at I is provided with a head I I and. a body portion, shaft or shank l2. It is longitudinally bored as at l3. A pin I4. extends through said bore 13 The pin 14 ismade fast at the shank end of the bore l3,'remote from the head ll, regardless of whether this bore extends completely through the bolt [0 or terminates short of the end thereof. Conveniently; although. other modes of utilization may be employed, the unstressed. pin 14 terminates flush with the outer surface of the head H of the bolt 10 when. the latter is-in its unstressed condition. When the bolt is tightened down into the particular workpiece, it undergoes stressing and elongates, as a result thereof. When it has been elongated to a predetermined and calibrated extent, the operator knows that it has been properly tightened. This is determined by measurement of the extent to which the. end of the pin l4 has apparently withdrawn within bore 13. This separation i5 is always the. same for a given stress and length of bolt grip.

It will be-observed in the foregoing that I provide no means in my said companion application Means are provided for causmechanical or electrical means.

for tightening down the bolt or stud. Reliance is made on hand-powered means. This has already been suggested herein as slow and tedious and as requiring nicety of judgment on the part of the skilled attendant. Mechanical, as distinguished from hand-powered, means is desirable for turning down the bolt.

One form of such mechanical means has heretofore been suggested wherein something akin to an overrunning clutch provides for slippage when the nut or bolt has been tightened to a predetermined stressing. For various reasons, however, including complexity, initial expense and comparatiye delicacy of the instrument, accompanied by high maintenance costs, widespread acceptance in the art of such construction has not been observed. In the highly practical means which I now disclose, tightening down of the bolt,

stud or other fastening means to a predetermined stress is accompanied by immediate and automatic de-energization with complete termination of all power impulses. No power is provided until at such time as the tightener is brought into play for tightening down other bolts or the like.

No waste of any sort occurs.

In the particular embodiment according to "Figure 3 of the drawings, the head ll of the bolt or stud I0 is gripped by the socket head I! of the power-operated tightener I8. This tightener I8 has a centrally disposed body portion I!) of enlarged diameter. Conveniently, and for reduc tion in quantity of material employed, as well as to decrease the weightv of the tightener l8" considered as a unit, I join the body portion l9 and the socket I! by a connecting portion 20 of appreciably' reduced section. In the design of this tightener, it is neccessary only that the diameter of .the connecting portion 20 be suflicient to impart requisite resistance in shear to the tightener.

I power body portion l9, and hence the' tightener itself, in any suitable manner as by fluid, The particular mode of powering which I employ does not itself form an essential part of my invention. It is apparent at once. that many suitable and entirely adequate and yet conventional expedients can be employed to this end.

To illustrate, I may readily install a motor, either hydraulic, air or electric, each with proper power leads, within the body portion [9, for example an electric motor as generally shown at ISA in Fig. 5. Inasmuch as I make no claim to the precise details. of such powering means, and claim the same only as an element of my new combination, I have done no more in the present disclosure than to make schematic illustration of such powering means.

It is an important feature of my invention that while bolt, studs and nuts of various contours, configurations, and cross-sectional dimensions are encountered, I can readily adjust my new tightener for use in connection therewith, simply by imparting removable and interchangeable characteristics to the socket portion H. To achieve this objective, therefore, I make the socket IT removable and replaceable with respect to the body portion 19 of the tightener 18, for exampleat 20A, a stem portion MB of socket H interfitting. a recessed end-portion IBA of power shaft-I8, being keyed thereto as at NC. This removable and interlocking feature can be achieved set screw may be employed, a chuck may be utilized, or a threaded connection employed with or without a set screw, the threads being turned so that the said socket I! will be self-locking in the direction of threading down the bolt or stud. Such means are of course conventional and need no further discussion at this point.

A bore 2I extends completely through the body portion I9 and socket I I. It is essential only that this bore 2| be in registry with the bore I3 of the bolt or stud II] when the tightener is ap plied on the head portion II thereof. For convenience, ease of machining, purposes of symmetry and the like, however, I find it highly advantageous from a practical standpoint to provide such longitudinal bores centrally, both of the bolt or stud and of the tightener. A rod 22 extends through the bore 2| of the tightener I8. It fits loosely therein. It is loosely guided in its longitudinal reciprocation through the tightener I8, however, by a suitable bushing 23 provided centrally in the recess of the socket I! and bored coaxially with respect to the bore 2| and the tightener I8, but of reduced section, only slightly greater than that of the rod 22. Thus, the rod 22 reciprocates with comparative freedom throughout the tightener I8, without binding therein, but is guided to follow closely the movements of the pin I3 of the bolt or stud l0.

Exteriorly of the body portion I9 of the power shaft I make a collar or plate 24 fast to the rod 22, so as to follow the movements of the latter in its reciprocation relative to the body portion I9. A coiled spring 25 serves to impel this collar, and hence the rod 22, in its sliding motion.

It will be seen, upon analysis, that to this point in the disclosure, power driven means have been described for turning down the bolt or nut IE. Moreover, a spring-pressed rod 22 forms part of the stud tightener. This rod extends through a bore 2I in'the tightener I8 and cooperates with and is forced into contact with the pin It in the bolt Ill. The spring 25 serves to urge the rod 22 into abutting engagement with the pin I4. The socket I! is removable with respect to the tightener I8, as noted above, so that the latter may be readily adapted for various sizes andcontours of bolt heads and similar items to be tightened.

No means have been described as yet, however, for causing the tightener to tension the bolt to predetermined extent, and thereupon to discontinue the power impulse to the tightener; Unnecessary wear and tear on the power sourceis thereby prevented, a saving in energy is accomplished, and the annoyance and possible hazard of the overriding or slipping clutch heretofore proposed is avoided, with the attendant requirement of constant supply of power.

To achieve this objective, I incorporate in the new assembly a micro-switch designated generally at 27 in Figure 3. This micro-switch is itself of conventional and Well-known design. Such switches are now on the market, and have a sensitivity or response to 0.0001 inch. One suitable switch for such purpose is now marketed by the Micro-Switch Division of First Industrial Corporation, of Freeport, Illinois. The details of this switch do not in themselves form part of this invention. The switch is installed as a unit, and should it fail for any reason, it is replaced as a unit. Accordingly the switch, indicated generally at 21, has a micro-switch plunger 28 associated therewith, mounted in the axial prolongationof the rod 22 in the tightener I8. A second collar or sleeve 29 is made fast to the micro-switch plunger 28. It is similar to the collar or sleeve 24 on the rod 22. The coiled spring 25 here= tofore described is disposed between the two collars and abuts thereagainst. The micro-switch 21 is mounted in a frame 39 disclosed in Figure 5, against which it thrusts.

As shown more fully in Figure 4, dials 3| and 32 are provided, rotatable against corresponding graduations 33 on the frame 39. In operation, the dial 3| is located so as to set the micro-switch 21 for the desired grip length, or extent of threading of the bolt or the like into the corresponding member into which it is seated. Similarly, the dial 32 is set for the required stressing of the bolt or the like for the given length of grip. These two adjustments have the effect of axially positioning the micro-switch plunger 28 relative to the corresponding end of the rod 22 and adjusting it into abutting relation against rod .22 for a determined stress.

In suitable manner, not herein disclosed since it does not per se form part of this invention, energization of a control means for the powerdriven tightener I 3 is brought about by the abutment of the micro-switch plunger 28 against rod 22. The tightener is free to rotate and begins to tighten down the bolt or stud Ill. As the bolt I0 is tightened down, it begins to elongate. A relative movement begins to occur between the unstressed pin I I and the surrounding body portion 52 and head I I of the bolt It. The combined eiiect is that the pin Id withdraws within the bore I3 from its initial position wherein its free end is flush with the outer face of the bolt head Under the impelling action of the spring 25 against collar 24, the rod 22 is forced to follow the pin I4, and to maintain its abutting engagement therewith. The efiect of this is to begin to unload the stressed spring 25. As he turning of the bolt It! continues and the latter is stressed and the length of bolt grip in the workpiece increases, the spring 25 is more and more unloaded. The exact point at which the spring becomes completely'unloaded has been previously determined through the adjustment of dials 3| and 32. Thus, during the course of the movement of the rod 22, the spring 25 becomes unloaded to such an extent that separation finally occurs between this rod 22 and the micro-switch plungerv 28. When this break occurs the supply of energy to the tightener i8 is terminated and the tightener becomes completely de-energized. It immediately stops rotating and remains in its completely deactivated condition. No energy is wasted.

Assurance is achieved that the bolt has been tightened with just the proper bolt grip; that is, the required number of threads have been turned down into the workpiece and the required stress placed upon the threads thus engaging with the workpiece.

The dials 3I and 32 in the embodiment here disclosed are logarithmic, although of course they may be calibrated for linear adjustability. They cause the switch to be so positioned that the rod 22 contacts the pin I4 and holds it in contacted condition until the stretch of the bolt causes the pin Hi to recede into the bolt or stud I 0 to such an extent that the follower rod 22 moves to the left in Figure 3 a distance sufiicient to separate the rod 22 and the micro-switch plunger 28.

It will now be in order to discuss the embodiment disclosed in Figure 6, wherein provision has been made for-associating my new tightener with a screw, bolt or nut having a hollow head. Therein the bolt indicated generally at IOA has a shaft l2. The enlarged. head HA thereof in section has the form and configuration of an annulus. This annulus is defined by a central recess 34 and the outer wall of the head HA. The bore I3 in the bolt [DA is basically similar to that in the construction according to Figure 3. The pin l4 likewise is identical with that of Figure 3. Initially, therefore, the outer extremity of the pin [4 is fiush with the transverse wall 34A at the bottom of the recess 34. The tightener [8A as provided in the embodiment according to Figure 6 carries at its working end, instead of the socket ll according to Figure 3, a male stud or prolongation 35 adapted to the contour of the head HA of the bolt IOA. As indicated generally at 36, the stud 35 is removably mounted on the tightener body portion 25, so that the tightener can be quickly adapted. simply by the insertion of a corresponding stud 35, for cooperation with bolts or studs IDA having any conventional configuration of head HA.

Finally, and having referenceto the embodiment according to. Figure '7, provision is made for turning a nut runner or the like 3.1 on a bolt or stud 38 fast on a suitable workpiece. Here a bore 133 extends through the bolt 38. Pin MB is fast at its inner end 39 in the bore BB and, when the bolt is in its unstressed condition, is flush at its outer end with the outerv extremity of the bolt 38.

The objective here of. course is to tighten the nut 31 down to such an extent as to stress the bolt 38 to a predetermined magnitude. The length of bolt grip is already determined by the number of threads within the nut 31. In this construction a recessed socket head HA is. provided at the working end of the body portion 25B of the tightener. As indicated at M, the socket head is formed separate from the body portion and may be interchanged to adapt the tightener for the handling of various sizes of nut runner and the like. A sleeve 42 is provided within an enlarged longitudinal bore 43 extending through the tightener 25B. This sleeve abuts against the end 40 of the bolt 38. It is impelled by a coiled spring 25C. At its free end the spring 250 is made fast to rod 22B by way of collarlZC and being under compression attempts to restrain the same into longitudinal movement following the pin MB of the bolt 38.

Following adjustment of the dials 3i and 32 of the micro-switch in the manner hereinbefore generally described with reference to the embodiment according to Figure 3, through tightening down the nut, contact is broken between the rod 22B of the tightener and the corresponding micro-switch plunger, not shown, but identical with that designated at 28 in Figure 3.

It will readily be seen from the foregoing that the new tightener is simple and reliable in construction, and while initially inexpensive, is sturdy and of long useful life. It is quickly adapted for handling bolts or studs of various conventional or uncoventional configuration, as for example, those having internally recessed heads. When the bolt is stressed to the proper extent the tightener is automatically taken out of operation. No waste power is consumed and no slippage occurs, resulting'in frictional wear. Should anything go awry with the micro-switch it can be readily and quickly replaced as a unit, itbeing of low first cost.

' One-of themost highly advantageous features of my new construction is that while extremely rapid in operation. it requires no output of energy onthe. partof. the operator. The tightener ispowered entirely by mechanical means as distinguished from manual means or hand power. The operator may be. of but moderate skill. No remiumis placed on the judgment and discretion of the, operator, the preliminary settings, which may be according to the'data on the drawings or specifications, being followed by subsequent automatic power cut-off when proper stressing and length of bolt grip has been achieved. By a simple re-design of the tightener it can be adapted for tightening down nut runners as distinguished from the conventional bolt or stud.

All these and many other highly practical results are achieved according to the practice of my invention. It will be readily understood from the foregoing that many modifications of the present embodiment will readily suggest themselves to those skilled in the art once this general disclosure is made available; and that similarly, many other embodiments, all falling within the scope of this invention, will likewise suggest themselves. Accordingly, I desire that the present disclosure be construedas merely illustrative, and not by way of limitation.

I claim:

1. A bolt or stud tightener for use with a stress-indicating bolt or stud having an unstressed indicator pin therein, comprising in combination, means for stressing said bolt or stud, means contacting said bolt or stud and including means contacting said indicator pin for sensing the movement of said unstressed pin relative to the bolt or stud as the latter is stressed, means for biasing said sensing means relative to said pin, and means for arresting movement of said stressing means when the bolt or stud has been stressed to a predetermined ex tent, with respect to said unstressed pin.

. 2. A bolt or stud tightener for use with a stressmdicating bolt or stud having an unstressed indicator pin therein, comprising, in combination, a body portion, a socket portion removably secured to said body portion, means for rotating said body portion, means contacting said bolt or stud and including means contacting said indicator pin for sensing the movement of said unstressed pin relative to the bolt or stud as the latter is stressed, means for biasing said sensing means relative to said pin, means for adjusting the stress of said biasing means against said sensing means, and means for breaking the connection between said adjusting means and said sensing means when the bolt or stud has been stressed to a predetermined extent, and thereby d'e-energizing the tightener.

3. A bolt or stud tightener for use with a stressindicating bolt or stud having an unstressed pin therein, which tightener comprises in combination a longitudinally-bored body portion, a rod extending through the longitudinal bore thereof into contact with the pin of the stud, a microswitch including a plunger contacting said rod, means for biasing said rod against said pin, means for adjusting the stress of said biasing means, and power means for rotating said body portion and incorporating an electric circuit including said rod and said adjusting means, turning of the body portion to a predetermined extent causing separation between said rod and said adjusting means.

4. A bolt or stud tightener for cooperating with a stress-indicating bolt or stud having an unstressed pin therein, which tightener comprises in combination a body portion, means for imparting rotary twist to the head of the bolt or stud and removably secured to said body portion, said body portion and said last-mentioned means being longitudinally bored, a rod extending through the longitudinal bore into contact with the pin of the stud, a sleeve or collar fast to said rod, an adjustable micro-switch disposed in a frame rigid with said body portion and having a micro-switch plunger, a collar or sleeve on said micro-switch plunger, a coiled spring abutting against said collars or sleeves and serving to force said rod into engagement with the pin of the bolt or stud as the latter is tightened down, and power means for rotating said body portion and incorporating an electric circuit including said rod and said adjusting means, turning of the body portion to a predetermined extent causing separation between said rod and said microswitch plunger.

5. A nut tightener for a bolt or stud having an unstressed pin therein, comprising a longitudinal- 25 1y bored body portion, a collar or sleeve in said bore, a rod extending longitudinally through said collar or sleeve, a coiled spring reacting against said collar or sleeve and adapted to force the same outwardly into engagement with a resistant portion of the corresponding bolt or stud against which the nut is being tightened, and spring means forcing said rod into engagement with the unstressed pin 01' said bolt or stud. 

